1. Field of the Invention
The present invention relates to printing apparatuses, printing methods, and computer programs, and more specifically, to a printing apparatus for printing on a non-recording surface of a recording medium that is detachably attached and rotatably driven, a printing method, and a computer program.
2. Description of the Related Art
A printing apparatus for printing information by dropping ink droplets from an ink droplet discharge nozzle for discharging ink droplets with respect to a non-recording surface of a disc-shaped recording medium such as CD, DVD, and Blu-ray disc (trademark) is known. A method of printing on the non-recording surface of the recording medium includes a method of moving the ink droplet discharge nozzle from the peripheral edge part towards the central part of the recording medium in a radial direction of the recording medium while rotating the recording medium, and dropping ink droplets onto the non-recording surface of the recording medium.
However, the discharge frequency from the ink droplet discharge nozzle for discharging the ink droplets is limited by factors such as temperature rise of the print head configured with the ink droplet discharge nozzle, ink refill, and stabilization of the meniscus. In view of such factors, the discharge frequency is assumed to be about 10 kHz in a bubble jet (registered trademark) type.
For instance, the distance from the center of the ink droplet to be dropped onto the outermost periphery of the printable region of the recording medium to the center of the recording medium is 60 mm, and printing is performed with the ink droplet on the outermost periphery at 600 dpi (about 42.3 μm). In this case, the number of rotations per one minute of the recording medium can be calculated as below.Linear velocity: 42.3×10−6 [m]×10×103 [1/s]=0.423 [m/s]Disc rotation number: 0.423 [m/s]×60 [s]/(120×10−3×π)[m]≈67.3 [rpm]
In order to control the discharge timing of the ink droplets from the ink droplet discharge nozzle, it is desirable to control by using a signal of an optical pickup for reading out data from the recording surface of the recording medium and recording data on the recording surface to simplify the configuration.
However, a spindle motor used in a typical optical disc recording and reproducing device is difficult to stably rotate at 100 rpm. This is because the number of rotations that becomes a reference when recording and/or reproducing the commercially available optical disc is defined by the type of optical disc. For instance, CDs are desirably rotated at 200 rpm, the DVDs at 600 rpm, and the Blu-ray discs (trademark) at about 1000 rpm.
A technique for solving such issue and performing printing on the non-recording surface of the recording medium is disclosed in, for example, Japanese Patent Application Laid-Open No. 2008-27535. In Japanese Patent Application Laid-Open No. 2008-27535, the discharge timing from the ink droplet discharge nozzle is controlled using the signal from the optical pickup, and printing in which dots in the circumferential direction are decimated (hereinafter also referred to as “decimated printing”) is executed over plural laps with respect to one radius position.